The Library of Congress has always been a great research tool. Terms of use for the site are as follows.

The Library’s mission is “to engage, inspire, and inform Congress and the American people with a universal and enduring source of knowledge and creativity.” The United States’ Library of Congress has a vast digital collection that includes various formats of media. These formats include audio and video recordings, books/printed materials, film, video, legislation, manuscripts, maps, notated music, newspapers, personal narratives, photos, drawings, software, web archives, and 3D objects. The site also includes plenty of educational resources that can be used to engage students. These materials include classroom materials like lesson plans that utilize primary sources.